The present invention relates to a device that secures the connection between a wheel and a bicycle fork dropout.
A typical bicycle frame has at least one bicycle fork for mounting a wheel to the bicycle. A typical fork has a pair of spaced apart fork legs (or at least one fork leg), each leg having a dropout at a first end. The dropouts have inner sides (facing each other), outer sides opposite the inner sides, and an elongated aperture formed therein to form a slot for receiving a wheel axle or skewer rod. The hub of the bicycle wheel is mounted on the skewer, and a wheel may be mounted on the bicycle frame by inserting the skewer into the slot.
Skewer-type quick release devices are commonly used for attaching wheel axles to bicycle fork dropouts. They are advantageous because they secure the wheel assembly to the fork yet permit fast engagement and disengagement of the wheel assembly with respect to the fork with a quick, simple step, such as the turning and loosening of a quick release lever. The diameter of the skewer is smaller than the width of the slot in the fork dropout so that the skewer may readily slide radially into the dropout.
A problem with these skewer rods arises when braking forces are applied to the wheel, and particularly when such braking forces are applied to the wheel by a bicycle disk brake. Disk brakes have typically been used in off-road and racing applications, both downhill and cross-country. Disk brakes include a brake disk mounted on the wheel adjacent the center of the wheel and a brake pad mounted adjacent the brake disk. The brake pad engages the brake disk to slow down rotation of the bicycle wheel. Due to the large forces that arise when the disk brake is applied to slow rotation of the bicycle wheel, the skewer and quick release assembly tends to be insufficient to hold the wheel hub assembly and dropout rigidly together and in their proper position. The hub assembly thus tends to shift with respect to the dropout during braking. As all bicycle hubs are mounted in the same area of the dropout and therefore experience similar forces, such slippage is a problem in all standard applications of disk brakes on bicycles. In addition, the large forces generated during braking and the resulting relative movement between the skewer and the dropout load the skewer such that the skewer may become weakened or damaged by the dropout.
One solution to the slippage problem is to knurl both the inside face of the fork dropout and the outside mating face of the hub. The friction created by this process may be sufficient to hold the dropout and hub in place in many instances. However, such a solution requires special manufacturing, or at least modification, of both the dropout and the hub and does not provide the level of secured attachment desired for rigorous braking applications. An attachment of a bicycle wheel to a bicycle fork dropout that relies on more than just frictional forces therefore would be desirable.